Development of health-based environmental screening levels for insensitive munitions constituents

Dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ) are constituents of insensitive munitions being developed to minimize the acute hazards associated with non-intentional detonation of warheads. Although a reference dose (RfD) has been established for NQ and occupational exposure levels have been developed for all three compounds, current state-of-the science methods were not used. Here we present the latest toxicity data and interpretations for NTO, DNAN, and NQ and use Bayesian Benchmark Dose modeling and a Bayesian approach to applying uncertainty factors to derive tolerable daily intake (TDI) values. A TDI of 0.02 mg/kg-d was calculated for DNAN based on extramedullary hematopoiesis in female rats. A TDI of 2.4 mg/kg-d was derived for NTO based on testicular toxicity in male rats. A TDI of 4.0 mg/kg-d was derived for NQ based on increased fetal resorptions in rabbits. These TDIs are generally an order of magnitude higher than previously developed reference values. These values can be used to inform public health, occupational safety, and product acquisition and stewardship decisions. Drinking water, soil, and tap water screening levels were derived for residential and worker exposure scenarios to help inform risk assessment decisions.